<div dir="ltr"><div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066">Hi Ron,</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066">I would try reducing the etch powers/parameters and develop a very low power recipe. Leave a few nanometers of oxide in the dry etch (making sure gold is not exposed) and the final mile oxide etch can be in the BOE.</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066">or Cr/Au/Cr instead of Cr/Au and then wet etch chrome. </div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066">Thanks & br,</div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066">vamsi </div><div class="gmail_default" style="font-family:verdana,sans-serif;color:#000066"> </div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Thu, Feb 18, 2021 at 8:35 AM Demis D. John <<a href="mailto:demis@ucsb.edu">demis@ucsb.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div style="font-family:georgia,serif;font-size:small">We would generally permit this, although discourage it for volume or more frequent use. But one time would be acceptable. We would recommend using a system equipped with a <a href="https://wiki.nanotech.ucsb.edu/wiki/Laser_Etch_Monitoring" target="_blank">laser etch monitor</a> to minimize overetch into the Au. </div><div style="font-family:georgia,serif;font-size:small">We could run this etch if you need it, using our <a href="https://wiki.nanotech.ucsb.edu/wiki/Fluorine_ICP_Etcher_(PlasmaTherm/SLR_Fluorine_ICP)" target="_blank">Fluorine ICP</a>. Since the Au will only be exposed for a short time, risk of sputtering in the tool is low. However, the Au will likely get sputtered onto the etched SiO2 sidewalls - which should be acceptable if the next step is further metallization through the via.</div><div style="font-family:georgia,serif;font-size:small"><br></div><div style="font-family:georgia,serif;font-size:small">Contact me privately if you want to discuss further.</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Feb 17, 2021 at 12:49 PM Reger, Ronald K <<a href="mailto:rreger@purdue.edu" target="_blank">rreger@purdue.edu</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">
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<p class="MsoNormal">Dear Colleagues,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">One of our faculty members has a process he needs to run in which nano-scale oxide definition is required to expose a gold contact pad. With our shared-use RIEs we are very concerned about Au contamination in our etch tools, particularly
for our electron device researchers. We’re seeking your input from your facilities whether you may have etch tools that allow Au processing for these specialty kinds of processes, and if you have a procedure for dealing with such contamination. A generic
sketch about what our faculty member needs is shown below. <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">So, have you dealt with this contamination issue with your multi-use tools before, and how do you deal with mitigating the contamination? Do any of you have a tool that could be used by this research group?
<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks very much in advance.<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Ron Reger<u></u><u></u></p>
<p class="MsoNormal">Birck Nanotechnology Center<u></u><u></u></p>
<p class="MsoNormal">Purdue University<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><b><i><u>Generic process steps</u></i></b>: <u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Fabrication need: metal connection to a sub-micron-size metal pad buried under <=50nm ALD oxide (HfO2 or Al2O3).<br>
<br>
Conventional fabrication steps (see sketch attached):<br>
(1) cover metal pad with etch-resistive metal, e.g. Au,<br>
(2) ALD-grow oxide (20-50nm),<br>
(3) define a sum-micron PMMA mask using e-beam lithography,<br>
(4) dry etch oxide with Au serving as a stop-etch layer (ICP-assisted etch using BCl3 or SF6 gases),<br>
(5-6) subsequent standard e-beam lithography to connect the exposed Au pad to the outside circuit.<br>
<br>
Problem: Au (or any other metal which forms non-volatile compounds in RIE system) may be problematic for some electron device processes and is restricted from being used in shared-use RIE oxide etchers.
<br>
<br>
Current work-around: for large (>10 micron) pads steps (3-4) can be performed by optical lithography + wet etch in HF. e-beam resists like PMMA are attacked by HF and this work-around cannot be used if sub-micron lithography is needed.<br>
<img width="1320" height="651" style="width: 13.75in; height: 6.7812in;" id="gmail-m_7546176299027855424gmail-m_-7804919056960682266_x0032_738A1FF-6C82-487B-A676-B0AB16519191" src="cid:177b297c66375cf86ca1"><u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><div dir="ltr"><font style="font-family:verdana,sans-serif;color:rgb(0,0,102)" size="2"><span style="color:rgb(102,102,102)"><br></span></font><p class="MsoNormal"><span style="color:black">___________________________________________________<u></u><u></u></span></p><p class="MsoNormal"><span style="color:black">N.P. Vamsi Krishna, PhD</span><u></u></p><p class="MsoNormal"><span style="font-variant:inherit;color:black;font-family:Arial,sans-serif;font-size:10pt;margin:0px;padding:0px;border:0px;font-stretch:inherit;line-height:inherit;vertical-align:baseline"><i><b>Staff Scientist</b></i></span><br></p><p style="margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif;color:rgb(32,31,30)"><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:10pt;line-height:inherit;font-family:Arial,sans-serif;vertical-align:baseline;color:maroon;background-image:initial;background-position:initial;background-repeat:initial">Pritzker School of Molecular Engineering, </span><span style="margin:0px;padding:0px;border:0px;font-variant:inherit;font-stretch:inherit;font-size:10pt;line-height:inherit;font-family:Arial,sans-serif;vertical-align:baseline;color:black"><i><b>The University of Chicago </b></i></span></p><p style="margin:0in 0in 0.0001pt"><span style="color:black;font-family:Arial,sans-serif;font-size:10pt;margin:0px;padding:0px;border:0px;font-variant:inherit;font-stretch:inherit;line-height:inherit;vertical-align:baseline"><i><b>Resident </b></i></span><font color="#000000" face="Arial, sans-serif"><span style="font-size:13.3333px"><b><i>Associate</i></b></span></font></p><p style="margin:0in 0in 0.0001pt;font-size:11pt;font-family:Calibri,sans-serif;color:rgb(32,31,30)"><span style="margin:0px;padding:0px;border:0px;font-style:inherit;font-variant:inherit;font-weight:inherit;font-stretch:inherit;font-size:10pt;line-height:inherit;font-family:Arial,sans-serif;vertical-align:baseline;color:black"><span style="color:rgb(128,0,0);font-size:13.3333px">Center for Nanoscale Materials, </span></span><b style="font-size:13.3333px;color:black;font-family:Arial,sans-serif"><i>Argonne National Laboratory </i></b></p><p style="margin:0in 0in 0.0001pt;color:rgb(32,31,30)"><font face="Arial, sans-serif"><span style="font-size:13.3333px">Phone: 1 (331) 757-8565</span></font></p></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div>